Duplicating stencil



. to provide a duplicating stencil for type- P'atented Mar. 28, 1933UNITED STATES PATENT oEFicE ms 'smon, or woman, GERMANY, nssren'on. 'ro13mm wnonnia'or mom.

onmumr, A conrona'non on (mam a a DUPLIGATIN G STENCIL H6 Drawing.Application am June 15, 1931, Serial No. 544,701, and' in Germany Aprila0, 1631.

This invention relates to improvements in duplicating stencils and amethod for producin the same.

t has been known to use, as a duplicating stencil, a fibrous and porousJapanese paper coated with a layer of hardened or nonhardened roteins towhich softening agents such as ycerine, sugar, fats, fatty acids, etc.haveieen added. Suzh duplicating sten- 1o oils have, hgvever, thedrawback that the softening agent added to the proteins is 1iable,during the storage of the stencil, to be exuded at the surface of thecoating in such quantities that the stencil will become sticky 15 andconsequently useless.- It is not possible to eliminate this drawback bydiminishing the amount of the softening agents added to the proteinsbecause a certain amount of said I softeners is required to keep thecoating plastic. If the amount of the softeners added to the proteins isless than a certain positive value, the coating will become hard andfull of cracks after a certain period of storage, so that it will beimpracticalto use it. Nor is it possible to eliminate completely thisprecipitation of softeners in the coating by mixing inorganic fillerstherewith, consisting, for instance, of bentonit or kaolin, as has beenproposed in prior art, because such pastes cannot prevent, withcertainty, this exudation for a sufliciently long time." The main objectof this invention is to eliminate the above-mentioned drawback and toprovide a duplicating stencil which can be safely stored for aconsiderable period of time and which has a coating that remains softand plastic during this storage.

A further object of this invention is to provide a stencil coatingcomprising pro- 40 teins and softeners mixed with substances b means ofwhich said softeners may be'equa 'ly distributed in the coating andsecurely bound therewith.

' A still further object of this invention is' fectivel writing andduplicating machines, which will not smear the types or case and dirtythe caoutchouc rollers .of sairfiiachines.

The above-mentioned objects can be realized b adding organic fillers asdistinguishe from inorganic fillers heretofore used, to the coating,such organic fillers consisting, for instance, of a very finely groundwood-flour, such as beechwood. Fugue sylvatica) or bamboo-wood (Am 0bambos), or of horn-dust, Lycopodium dust or other substances.

Horn dust is derived by powdering or grindigg the horn material ofanimals, while Lycop ium dust (lycopode) is a yellow powder derived fromthe spores of the club moss, especially L. claoatum, L. selago, L.phlegmasia, L. mbmm, L. saussum, etc.

An or anic filler of this kind will efind the softeners within thecoating an will further the even distribution of such softeners.Duplicating stencils provided with a c'oatingin accordance with thisinvention remain uniformly soft and flexible even after having beenstored for a very long time and the precipitation of softeners istotally prevented. This is not the case with duplicating stencilsprovided with a protein coating as known in prior art, which becomesticky after a certain period of, storage or hard when the coating doesnot contain a sufiicient amount of softeners.

' A further advantage of adding an organic paste to the stencil coatingresides in the fact that when the duplicating stencil is used inconnection with a typewriter the types will not become dirty or locked.Furthermore, the softeners forming partof the coating and consisting ofoils or fats will not be deposited on the rubber rollers of thetypewriters and v duplicating mechanisms.

I have found thatthebest resultsare obtained when an organicfillerconsisting of a wood-dust is addedto the coating substance and used inconnection with other substances. u I

An example of a mixture which may be emplayed 1s as follows: Puts Water200 This liquid mixture is applied in the usual way onto a sheet ofJapanese paper at the usual temperature, of about 50 C. and is driedthen at the same temperature so that the water. evaporates.

The advantageous results obtained from the use of organic fillers, suchas Wood flour, are achieved owing to the fact that the wooddustcomprises a certain small amount of coagulating or tanning substanceswhich have a slight hardening efiect on the proteins contained in thecoating substance.

It is possible to increase the hardening efiect by adding anothersubstance, for instance, a formaldehyde, to the'coating.

I claim: I

. l, A process for manufacturing duplicat- Y ing stencils, comprisingthe steps of adding a substantially insoluble organic filler to'acoating mixture containing proteins and softening agents, and thenapplying said coating mixture onto a fibrous and porous sheet 2; Aprocess for manufacturing duplicating stencils, comprising the steps ofadding a a wood-dust to a coating mixture containing proteins andsoftening agents, and then applying said coating mixture; onto a fibrousand porous sheet.

3. A process for manufacturing duplicat-v ing stencils, comprising thesteps of adding horn-dust to a coatingmixture containing proteins andsoftening agents, and then applymg said coating mixture onto a fibrousand porous sheet.

4. A process for manufacturing duplicating stencils, comprising thesteps of adding a substantially insoluble organic filler to a coatingmixture containing proteins and softening agents then adding aformaldehyde to the mixture, and then applying said coating mixture ontoa fibrous and porous sheet.

7. A coating for duplicating stencils, comprising a mixture of petroleumjelly, a sul= phonated non-mineral oil, gelatine, a wooddust,g'lycerine, castor oil, olive oil, methylene blue and sodium parachlorbenzoate.

8. A coating for duplicating stencils com prising, 60 parts by weight ofpetroleum jelly, 18 parts by weight of a sulphonated non-mineral oil, 10parts by Weight of gela-z tine glue, 10 parts by weight ofa Wood-dust,

3 parts by Weight of glyc'erine, 2 parts by weight of castor oil, 2parts by Weight of olive oil, .7 5 part by weight of methylene blue and35 part by weight of sodium parachlorbenzoate. p 9. A coating forduplicating stencils comprising a mixture of hardened gelatin, asoftening agent and a permanent finely divided substantially insolubleorganic filler.-

10. A coating for duplicating stencils comprising a mixture of hardenedgelatin, a softening agent and a powdered organic filler containingsmall quantities of a tanning ma terial. i

11. A coating for duplicating stencils comprising a mixture of hardenedgelatin, a softening agent and a powdered cellulose filler.

12. A coating for duplicating stencils com prising a mixture of hardenedgelatin, a softening agent and one of a group of powdered organicfillers, said group including beechwood flour and bamboo wood flour.

In testimony whereof I have aifixed my Lycopodium dust to a coatingmixture containing proteins and' softening agents, and then applyingsaid coating mixture onto a fibrous and porous sheet,

5. A process for manufacturing duplicating stencils, comprising thesteps of adding a substantially insoluble organic filler to a coatingmixture containing proteins and softening agents, then adding ahardening agent to the mixture, and then applying said coating mixtureonto a fibrous andporous sheet. 7

6. A process for manufacturing duplicat-

